Field of the Invention
The present invention relates to an inkjet printing apparatus and an inkjet printing method.
Description of the Related Art
There is conventionally known an inkjet printing apparatus that uses a print head having print element arrays in which a plurality of print elements generating energy for discharging inks is arranged to apply a driving pulse to the print elements and drive the print elements so that the inks are discharged onto a printing medium to print an image. In such an inkjet printing apparatus, it is known that the driving pulse is formed from a pre-pulse for raising the temperature of the inks so as not to discharge the inks and a main pulse for discharging the inks.
It is known that, as the temperature of the inks near the print elements at the time of discharging the inks becomes higher, the viscosity and surface tension of the inks near the print elements may vary to increase the discharge amount of the inks. This may lead to deterioration in the quality of images to be printed according to the temperature of the inks at the time of discharging. To handle this problem, Japanese Patent Application Laid-Open No. H5-31905 discloses a technique by which a driving pulse table defined by a plurality of driving pulses different in the pulse width of the pre-pulse is used such that the driving pulse with a smaller pulse width of the pre-pulse is selected from the driving pulse table when the temperature of the inks is higher and the selected driving pulse is applied to the print elements. According to the description in the literature, even when the temperature of the inks varies, the discharge amount of the inks can be controlled to be almost constant, thereby suppressing deterioration in image quality.
In the manufacturing process of the print head, a manufacturing error of the discharge ports may occur to cause the deviation of the discharge amount of the inks from the print elements from a desired amount. This may cause the deterioration of quality of images to be printed.
For example, if a manufacturing error occurs so that the discharge amounts from all the print elements in the print element arrays are larger than the desired amount, when the driving pulse is applied to the print elements according to the technique described in Japanese Patent Application Laid-Open No. H5-31905, the images printed in all printing areas on the printing medium have higher densities than a desired one.
In addition, the likelihood of occurrence of manufacturing error of the discharge ports described above varies depending on the position in the print element arrays. For example, it is known that, in the manufacturing process of the print head, a manufacturing error may occur frequently in particular such that the discharge amounts from the print elements at the end portions of the print element arrays become larger than the desired one. In this case, the images with higher densities than the desired one are printed in the area on the printing medium printed by the print elements at the end portions of the print element arrays, which results in deterioration of image quality.